This research seeks to define the role and mechanisms in which indole and catecholamines affect neuroendocrine systems. Primary attention will focus on the hypothalamo-hypophyseal gonadotrophic axis controlling ovulation, and related reproductive functions. The laboratory rat will be the major focus of research, however, use of the guinea pig for selected experiments will allow a comparison of important results in the rat to a species with a true luteal phase and longer estrous cycle. Most of the emphasis will be on specific serotonergic and catecholaminergic terminals which are thought to be physiologically important in ovulation control. Chemically specific neuronal activity will be estimated in acute studies using an in vitro uptake system involving hypothalamic nuclear regions. Chronic studies will employ intracranial injection of specific neurotoxins and measurement of LH fluctuations via indwelling carotid cannulae. This type of in vivo system using intracranial push-pull cannulae will permit more detailed analysis of transmitter interactions by monitoring the effects of specific neurotoxins on critical hypothalamic regions during parallel blood collection for LH measurement. We believe that improved knowledge concerning these mechanisms in several species will shed new light on their control and lead to new models for research and new approaches in solving human neuroendocrine and reproductive problems in development, health and disease.